Pacific Ocean: French Polynesia (France)

Like the Hawaiian Islands, the tropical Marquesas Islands are extremely isolated and all flora and fauna present are the result of long-distance colonization and in situ evolution for thousands to millions of years. Forty-two percent of the 320 native vascular plants are endemic. The terrestrial snail community is quite diverse, with at least 78 species represented. Ten endemic birds occur here. Unfortunately, this biodiversity has been exposed to almost two millennia of human disturbance. Several species have gone extinct in known history and much of the flora and fauna is critically endangered.

Scientific Code

(OC0108)

Ecoregion Category

Oceania

Size

400 square miles

Status

Critical/Endangered

Habitats

Description Location and General DescriptionThe 12 Marquesas Islands are located approximately 5,500 km west of South America at 8º to 11ºS latitude and 139º to 141ºW longitude. All islands in the group are volcanic high islands with the northwest islands being approximately 6 million years old, and the southeast are the youngest at 1.3 million years old (Florence & Lorence 1997). The topography is very steep with knife-edged ridges, deeply dissected gorges and cliffs extending from mountaintops straight to sea level. Southeast trade winds are fairly constant year-round and moderate the rainfall and temperature, but long droughts can occur during El Nino cycles (Florence & Lorence 1997). Variation in topography and orientation produces variation in annual rainfall throughout the islands, ranging from 500 mm on lowland leeward coasts to more than 4,000 mm above 1,000 m on the five highest islands. Eastern upland areas tend to be wettest and coolest with mean temperatures from 15° to 25oC while western lowlands are drier and hotter with temperatures averaging 25° to 29oC. (Adamson 1936).

Biodiversity FeaturesThe Marquesas are among the most isolated archipelagos in the world and thus have a highly endemic biota. The islands support 320 native vascular plant species with 42 percent endemism, including two endemic genera (WWF & IUCN 1995, Florence & Lorence 1997). There are approximately 200 introduced plant species. A number of genera including Asplenium, Psychotria, Bidens, Cyrtandra, Peperomia, Myrsine, Cyperus, and Melicope have numerous endemic species that evolved in the Marquesas from single ancestral species (Wagner 1991). The fern flora is particularly rich (WWF & IUCN 1995). Three plant species have become extinct and 16 species are endangered (Dahl 1980). The islands support a fairly rich invertebrate fauna with a notable diversity of at least 78 land and freshwater snail species and 16 fruit fly (Drosophila) species (Adamson 1935).

The Marquesas support 19 breeding seabird species and 11 resident land birds. The endangered ultramarine lory (Vini ultramarina) has declined from an archipelago-wide distribution prehistorically to only the island of Ua Huka recently (Steadman 1989, Kuehler et al. 1997, Stattersfield et al. 1998). Today, a translocation program has reestablished a population on Fatu Hiva which is free of alien black rats (Rattus rattus) thought to be a major factor in its decline elsewhere (Keuhler et al. 1997). The red-mustached fruit-dove (Ptilinopus mercierii) has become extinct and the Nuku Hiva pigeon (Ducula galeata) has a population of fewer than a few hundred birds on Nuku Hiva Island (Dahl 1980). Other threatened or endangered endemic bird species include the Marquesas ground-dove (Gallicolumba rubescens), Marquesas kingfisher (Halcyon godeffroyi), Fatuhiva monarch (Pomarea whitneyi), Iphis monarch (P. iphis), and Marquesas monarch (P. mendozae)(Dahl 1980).

Current StatusHuman habitation has influenced Marquesan ecosystems for millennia. Polynesians colonized the islands between 1,000 to 2,000 years ago. They reached a population peak of about 80,000 inhabitants several hundred years ago which was accompanied by the destruction of most lowland vegetation and in the formation of grassland in drier, frequently burned areas (Rolett 1993). The archaeological work in the Marquesas has revealed an extensive history of extinction and extirpation of birds (Steadman & Rolett 1996). Excavations on Ua Huka show that the island once supported 7 more seabird species than are present today and 13 land birds that are now gone, including 10 endemic rails, pigeons and parrots (Steadman 1995). Summary of all archaeological work indicates that 10 land birds became extinct and 7 bird species were extirpated from most of their range (Steadman & Rolett 1996). All remaining endemic birds are considered threatened, some critically (Stattersfield et al. 1998).

Designation of conservation areas in the Marquesas must be accompanied by major control efforts for alien species and fire, and habitat restoration efforts. Two reserves, Eiao Island and the dry forest reserve on Mohotani, have been so totally denuded by feral sheep and other animals that rainfall washes away so much soil that plants cannot regenerate (Montgomery et al. 1980). Introduced great horned owl and common myna are thought to greatly impact native bird species on Hiva Oa (Stattersfield et al. 1998). In addition to mammals, birds, and rats, the introduced plant Miconia magnifica is established and spreading. It has the potential to completely replace all native forest as its congener has done in parts of Tahiti (Montgomery et al. 1980). Hunting is a major factor in the endangerment of the Nuku Hiva or Marquesan imperial-pigeon, a species with less than 300 individuals left (Stattersfield et al. 1998).

Types and Severity of ThreatsLowland forests were completely replaced with introduced species (Florence & Lorence 1997). Following European contact, introduced diseases wiped out all but approximately 3,800 Polynesian inhabitants. The subsequent introduction of herbivorous and predatory mammals has had an even more catastrophic effect on upland flora and fauna (Rolett 1993). Frequent fires have also transformed many natural habitats and works to maintain introduced communities. Uninhabited islands, such as Hatutaa, that are protected from human habitation and mammals still support large numbers of seabirds and land birds, but few areas of natural forest are currently included in the reserve system (Dahl 1980).

Justification of Ecoregion DelineationThis ecoregion consists of the relatively discrete Marquesas Islands group. Allison treats the Cooks, Societies, Tuamotus, and Marquesas as a unit herpetologically as they share a similar reptile assemblage. Van Balgooy (1996) similarly lumps the Cooks, Niue, Societies, Tuamotus, Tubaui, and Marquesas based on floristic affinities. However, Birdlife International (Stattersfield et al. 1998) separates the Marquesas from surrounding island groups due to the presence of 10 endemic bird species, and based on this consideration we have delineated the Marquesas as a separate ecoregion.

ReferencesAdamson, A.M. 1935. Affinities and origins of the fauna of the Marquesas Islands. PhD dissertation University of California, Berkeley. 205 pp.

Wagner, W.L. 1991. Evolution of waif floras: a comparison of the Hawaiian and Marquesan archipelagos. Pages 267-284 in E. Dudley, editor. The Unity of evolutionary biology. The proceedings of the 4th International Congress of Systematics and Evolutionary Biology. Dioscorides Press, Portland, Oregon.